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Newsgroups: comp.os.386bsd.development Path: sserve!newshost.anu.edu.au!munnari.oz.au!news.Hawaii.Edu!ames!elroy.jpl.nasa.gov!decwrl!netcomsv!netcom.com!jmonroy From: jmonroy@netcom.com (Jesus Monroy Jr) Subject: Re: [FreeBSD 1.0R] DMA Problems? Message-ID: <jmonroyCI6IIM.IFz@netcom.com> Organization: NETCOM On-line Communication Services (408 241-9760 guest) X-Newsreader: TIN [version 1.1 PL8] References: <CI6291.HBA@genesis.nred.ma.us> Date: Fri, 17 Dec 1993 12:25:34 GMT Lines: 45 steve2@genesis.nred.ma.us wrote: : I originally asked the question so hopefully I can clarify things a bit. : : :: [deleted stuff] :: : : >>In fact, i'm also experiencing lotta DMA overruns when attempting to do : >>some floppy IO while some heavy compile job is running. This is in a box : >>with an Adaptec SCSI, and i didn't track it down whether it's the CPU : >>load that causes the trouble (would really look strange to me), or if : >>it's the heavy disk IO that happens while compiling. : That doesn't appear to be the case. The buffer is pre-loaded for the : write, and there doesn't have to be any other disk transfers going on : for the problem to happen. This is why I'm still a little baffled. Only : three things need to go on for an overrun: an FDC DMA write (device read), : another busy process running with the transfer, and possibly video I/O. In : fact, video is my next suspect. : Boy, after all this discussion it's plain that some people have not heard a word I've said about this problem in the past. 1) I presented not only written evidence, but third party verification of the problem (with solution). 2) I presented a program to verify my claims, but no seems to have seen the program. 3) I presented the fix.. and still no one listens. The problem (to the root) is lack of BUS time. If the FDC does not get an ACK from the DMA controller in time, it simply stops and reports the error. RTF Data Guide. e-mail me if you need a page number. -- Jesus Monroy Jr jmonroy@netcom.com Zebra Research /386BSD/device-drivers /fd /qic /clock /documentation ___________________________________________________________________________